Like the title says, do I need a special hardware other than my laptop's default wireless card to crack a wep key from auditing network ?
Additionally, what is the exact software needed and do I need a different operating system than Windows?
If you are trying to crack a wirless network (i.e. a WEP key) using packet injection, you will need a network card that can actually inject packets. LifeHacker has a tutorial which shows you how to crack a WEP-encrpted network using a live ISO of BackTrack Linux, which is a security and penetration-based-distro. You could probably run AirSnort (or similiar equivalents) on Windows but I would, personally, prefer Linux or BackTrack.
I have used BackTrack sucessfully on (my own, controlled) WEP-encrypted network. Bear in mind it takes a lot of packets to be captured before you can even guess at the key.